Iron oxide nanocube assembly on silver nanowire templates to enhance magnetic hyperthermia performance

Iron oxide nanocubes (IONCs) represent one of the benchmark magnetic nanoparticles able to most efficiently convert magnetic energy into heat for magnetic hyperthermia cancer treatment, and their heat losses can be further increased by controlling their assembly through the synthesis of ordered structures. However, achieving the alignment of nanoparticles with one-dimensional chain or columnar structures into long arrays to then study their magnetic heat losses still remains a significant challenge. This study exploits silver nanowires as high-surface-area anisotropic templates for the controlled chaining of IONCs. The surfaces of the IONCs were purposely functionalized with polyethyleneimine (IONCs@PEI) and interacted with silver nanowire (AgNW) surfaces via electrostatic attraction. Here, alternating current (AC) magnetometry was employed to compare the heating performance expressed as specific absorption rate values between individually coated IONCs@PEI and AgNWs@IONCs@PEI composites at various magnetic field strengths and frequencies. SAR values reveal that clustering of IONCs on AgNW surfaces improves the heating efficiency at an applied magnetic field strength of 24 kA m^-1, regardless of the applied frequencies, with SAR values of AgNWs@IONCs@PEI composites outperforming those of individual IONCs@PEI. Moreover, dynamic hysteresis loops showed that the coercive field of AgNWs@IONCs@PEI increased significantly at 24 kA m^-1, indicating the existence of strong magnetic dipolar interactions between nanoparticles. This study shows an innovative approach for guiding the orientation of magnetic nanoparticles using one-dimensional templates to enhance their heating performance.